In hardy areas, crape myrtles break dormancy around March and bloom from early summer to fall. They produce flowers on new wood and thus should be pruned in February.
Crabapple trees require minimal pruning, and you can make any necessary cuts on your trees after they go dormant in the late winter or the early spring before bud break.
Some hydrangeas bloom on last year's growth, and some bloom on new wood that emerges in the spring. Don’t prune the former type in the fall, or you risk losing blooms.